Safety device for materials hoist



Feb. 1, 1966 K. J. w. MERSON 3,232,381

SAFETY DEVICE FOR MATERIALS HOIST Filed March 4. 1964 INVENTOR KAROL J. W. MERSON Y- 427212510 1 ATTO R N EYS United States Patent 3,232,381 SAFETY DEVICE FOR MATERIALS HOIST Karol J. W. Merson, Toronto, Ontario, Canada, assignor to Anthes Imperial Limited, Saint Catherines, Ontario, Canada Filed Mar. 4, 1964, Ser. No. 349,244 6 Claims. (Cl. 187-83) This invention relates to materials hoists for construction towers, and is particularly concerned with a brake mechanism for automatically stopping the fall of a hoist upon an accidental loss of the hoisting or holding force.

The brake mechanism in accord with this invention is adaptable to materials hoists in which the carriage is guided by upwardly extending tracks with the lifting force being provided through a cable. This type of hoist is commonly used in temporary construction towers, and it has been found that such towers often lose their vertical alignment with the result that the guide tracks for the hoist are warped.

While most materials hoists now in use are provided with some type of automatic braking means, experience has proven that misalignment or warping of the guide tracks often results in failure of the braking mechanism. Most of the known mechanisms operate on the principal wherein failure of the lifting force automatically causes a jamming device to become wedged between the hoist and the guide track or tracks as to stop the downward fall of the hoist carriage. It has been found, however, that should the lifting force fail with the carriage at a position adjacent a warped extent in the guide tracks, the known braking mechanisms fail to operate. The failure of the braking mechanism immediately upon loss of the lifting force, allows the speed at which the carriage drops to build up very quickly so that the braking mechanism cannot halt the downward fall of the carriage even though the guide tracks straighten out below the point of failure.

In accord with the present invention, it is recognized that the failure of the prior braking mechanisms has been due to their failure to adapt to warped guide tracks. It has further been recognized that this failure to adapt is due to the fact that the known devices are ridigidly connected to th hoist carriage. Due to this rigid connection, the jamming mechanisms of these prior saftey brakes are positioned relative to the guide tracks by the position of the carriage rather than by the actual position of the guide tracks at the level of the brake mechanism. For example, should the guide track be outwardly warped at the position of the brake mechanism, the jamming device will fail to operate.

It is an object of this invention, therefore, to provide an improved brake mechanism for materials hoists.

It is a more specific object of the invention to provide brake mechanisms for materials hoists which are capable of adapting themselves to warped or misaligned guide tracks.

It is a further object of the invention to provide a braking mechanism which is not rigidly connected to the carriage of the hoist, so that the jamming mechanism carried by the brake is always positioned the proper distance from the guide tracks for effective operation.

The invention will be more thoroughly understood from the following description of a preferred embodiment thereof as read in conjunction with the accompanying drawings.

In the drawings:

FIGURE 1 is a perspective view, partly broken away, of a preferred embodiment of the braking mechanism for a materials hoist in accord with this invention.

FIGURE 2 is an enlarged view of a portion of the mechanism shown in FIGURE 1.

Referring to FIGURE 1, the brake mechanism is generally indicated by the reference numeral 10. It is connected to a cable or the like 12 through which the lifting force is transmitted from a source of power which is not shown and forms no part of this invention. As is well known to those familiar with materials hoists, cable 12 would be connected to a motor located at the top of the tower or at ground level through appropriate sheaves and/ or drums.

Two guid tracks 14 extend upwardly along opposed sides of the tower and in this regard, it will be recognized that while only two guide trancks are illustrated, a larger tower might employ four guide trancks. Not shown, but suspended from the lower end of brake mechanism 10 is a carriage. In this illustrated embodiment, the carriage is connected to the lower ends of the hangers 16, the latter being pivotally attached to a pair of linkages 17 which are, in turn, pivotably attached to the brake mechanism.

Brake mechanism 10 includes a main load-bearing memher which extends transversely between the guide tracks 14 but which does not actually engage the guide tracks. This load-bearing member consists of a pair of side by side beams 20 interconnected by welded tie bars 22. Suspended from each end of the transverse load-bearing member, are flange engaging elements 24 which interconnect the load-bearing member with the flanges 26 of the guide tracks 14. These flange engaging elements each consist of parallel spaced generally triangular shaped plates which are interconnected by a welded interval curved cam 30. Actual engagement with flanges 26 of guide tracks 14 is effected through the welded vertically extending bars 32.

An important feature of the illustrated brake mechanism is the type of connection between the flange engaging elements 24 and th transverse load-bearing member 20-20. As shown, these elements 24 are suspended from each end of the load bearing member by parallel linkages 40. These linkages are pivotally connected to both the elements 24 and the transverse member 20-20 so that the elements 24 are capable of shifting laterally relative to the load bearing member 20-20. By this means, the jamming mechanisms consisting of the rollers 74}, which are described in detail hereinafter, are always positioned relative to the guide tracks 14 and cams 30 for proper jamming action therebetween. It can be seen, therefore, that through the use of the parallel linkages 40 and the linkages 17, there is incorporated within the breaking mechanism, sufficient flexibility to accommodate warping or misalignment in the guide tracks.

Referring still to FIGURE 1, it will be noted that the cable 12 whos lower end is shown positioned above load bearing member 20-20 for clarity in illustration, will be connected for operation, to the transverse pin-type linkage 46. Each end of linkage pin 46 is mounted for vertical sliding movement relative to transverse member 20-20 in the slots 48, only one of which can be seen in FIGURE 1. These slots are formed partially in the members 20 and partially in the upstanding ears 21 which are rigidly connected to members 20. Pin linkage 46 carries a U- shaped bracket 50 to which is rigidly connected a downwardly extending rod 52. A coil spring 54 is positioned on rod 52 and biases the rod downwardly through the exertion of spring pressure between the collar 56 carried at the lower end of the rod and the transverse plate 58 bearing against the underside of transverse member 20-20. It can be seen, therefore, that when cable 12 is connected to the slidable linkag 46, the bias of spring 54 is normally overcome so that the linkage 46 is normally positioned as shown in FIGURE 1, i.e., at the top of slots 48. A reduction in the lifting force transmitted to cable 12 as by breakage of the cable or slippage of the cable on its winding drum, causes linkage 46 to be moved down- & wardly relative to transverse member 2t)20 under the influence of spring 54.

Also connected to pin linkage 46 is a pair of tie bars 60, whose lower ends are pivotally connected to the inner ends of a pair of rocker arms 62. The latter elements each actually consist of two rocker artms interconnected through the pins 64, 66 and roller axles 68. It can be seen, therefore, that as the pin linkage 46 moves downwardly relative to the load bearing member 2020, the inner ends of the rocker arms 62 are also lowered with the further result that the outer ends of these rocker arms are raised as to cam the rollers 70 between the guide tracks 14 and the cam members 30. This jamming action can best be seen in FIGURE 2, and is an effective break against downward movement of the braking mechanism and suspended carriage.

As indicated above, it is the flexible interconnection between the various components forming the brake mechanism in accord with this invention which achieves the object of the invention, namely, to arrest the fall of the hoist carriage upon reduction of the lifting force through cable 12 despite misalignment or warping in the guide tracks 14. It is this flexible interconnection which guarantees that the braking mechanisms will be properly positioned relative to the guide tracks for immediate effective operation at all times.

What I claim as my invention is:

1. A brake mechanism for a materials hoist, said hoist including upstanding guide tracks and a carriage suspended from said brake mechanism and cable means for exerting an upwardly directed lifting force on said brake mechanism whereby said carriage may be raised and lowered; said brake mechanism comprising a transverse load bearing member extending between but not contacting said guide tracks, a .pair of guide track engaging brake devices carried one at either end of said load bearing member, first linkage means flexibly connecting said brake devices to said load bearing member, second linkage means flexibly connecting said carriage to said brake devices, means for actuating said brake devices, third linkage means connecting said brake devices actuating means to said cable means whereby said brake devices actuating means is normally held inoperative and spring means for automatically causing said brake devices actuating means to actuate said brake devices upon the loss of said lifting force.

2. A brake mechanism as claimed in claim 1, in which said first linkage means comprises arm members pivotally connected at one end to said load bearing member and at their other ends to said brake devices whereby said brake devices are adapted to move relative to said load bearing member as to fol-low said guide tracks freely.

3. A brake mechanism as claimed in claim 2, in which said second linkage means comprises a pair of arm members pivotally connected to said brake devices at one end and to said carriage at their other ends whereby said brake devices are adapted to move relative to said carriage as to follow said guide tracks freely.

4. A brake mechanism as claimed in claim 3, in which each of said brake devices includes cam plates and rollers, said means for actuating said brake devices consisting of a pair of lever arms carrying said rollers at one end, pivotally connected to said brake devices intermediate their ends and pivotally connected to said third linkage means at their other ends whereby rocking of said lever arms about their pivotal mounting on said brake devices causes said rollers to jam between said cam plates and said guide tracks whereby to halt downward movement of said brake mechanism and the carriage attached theretO.

5. A brake mechanism as claimed in claim 4, in which said third linkage means comprises a pair of tie bars pivotally connected at their lower ends to said lever arms and attached at their upper ends to said lifting force exerting means, said spring means being positioned relative to said tie bars and said load bearing member as to bias said tie bars downwardly relative to said load bearing member with said lifting force norm-ally exerted upwardly against the bias of said spring means.

6. A brake mechanism as claimed in claim 5, in which said first linkage means comprises a total of four arm members pivotally connected at their upper ends to said load bearing member and at their lower ends to said brake devices.

References Cited by the Examiner UNITED STATES PATENTS 1,027,840 5/1912 Graham 187-73 1,151,854 8/1915 Bartos 187-84 2,326,046 8/1943 McCormick 18788 SAMUEL F. COLEMAN, Primary Examiner, 

1. A BRAKE MECHANISM FOR A MATERIALS HOIST, SAID HOIST INCLUDING UPSTANDING GUIDE TRACKS AND A CARRIAGE SUSPENDED FROM SAID BRAKE MECHANISM AND CABLE MEANS FOR EXERTING AN UPWARDLY DIRECTED LIFTING FORCE ON SAID BRAKE MECHANISM WHEREBY SAID CARRIAGE MAY BE RAISED AND LOWERED; SAID BRAKE MECHANISM COMPRISING A TRANSVERSE LOAD BEARING MEMBER EXTENDING BETWEEN BUT NOT CONTACTING SAID GUIDE TRACKS, A PAIR OF GUIDE TRACK ENGAGING BRAKE DEVICES CARRIED ONE AT EITHER END OF SAID LOAD BEARING MEMBER, FIRST LINKAGE MEANS FLEXIBLY CONNECTING SAID BRAKE DEVICES TO SAID LOAD BEARING MEMBER, SECOND LINKAGE MEANS FLEXIBLY CONNECTING SAID CARRIAGE TO SAID BRAKE DEVICES, MEANS FOR ACTUATING SAID BRAKE DEVICES, THIRD LINKAGE MEANS CONNECTING SAID BRAKE DEVICES ACTUATING MEANS TO SAID CABLE MEANS WHEREBY SAID BRAKE DEVICES ACTUATING MEANS IS NORMALLY HELD INOPERATIVE AND SPRING MEANS FOR AUTOMATICALLY CAUSING SAID BRAKE DEVICES ACTUATING MEANS TO ACTUATE SAID BRAKE DEVICES UPON THE LOSS OF SAID LIFTING FORCE. 